Heat wave E420, 96 outside, 110 stop and go!
 

Damn this 97 E420 runs hot! In this heat wave when it's 96 outside, the E429 is fine on the highway running around 90 degrees. When I'm driving stop and go with the A/C on, the engine is registering an alarming 110 degrees! My aux fan is working and kicking in but this scares me as it's the wifey's main driving car and she doesn't look at the instruments like I do. She won't turn off the A/c at stops, recirculate the inside air, etc. What can I do? Is Water Wetter a good solution or is it just marketing hype?

That sounds too hot. I'd check the coolant/water mixture; you don't want stronger than 50/50, and surprisingly most cars I check are. I run a 40/60 coolant to water ratio and Water Wetter, which does seem to help. Check the rubber on the coolant jug cap and make sure the fan doesn't freewheel when you shut the engine off hot. Here's a great web site and this link explains how to modify the fan clutch so it "kicks on" at a lower temperature. I fought high temps on my coupe and this mod made a huge (15°C) difference.

Maybe its time for the cool harness modification.
http://pages.prodigy.net/jforgione/MB_CTS.html

I live in the Palm Springs, CA area where summer days are pushing 110F. My '95 E420 rarely breaks 90C even in stop and go driving with the AC in full array. I recently took 4 Marines with their luggage from the airport back to their base. It is a 65 mile trip starting up a long grade into the high desert. Even up this grade the car temp stayed a little over 90C then dropped back below 90C
There is a new thermostat, water wetter and less than a gallon of coolant, the balance water. I am one happy camper!
Anziani
'93 300CE 188K
'95 E420 122K

The M119's can run a bit hot. 110C is not too hot!

That being said, my 94 hasn't broken 100C. Make sure the fan clutch is working properly..


Michael